The invention relates to a printer head bank for a printer used as an output unit, as for example, for a personal computer and the like.
Printer head banks used as output units for personal computers and the like have been heretofore fabricated in the manner shown in FIGS. 1-3. In FIGS. 1, 2 and 3 numerals 10, 11 and 12 designate a head carriage, permanent magnet, and a yoke, respectively. Numerals 13, 14, 15 and 16 denote coils, typing hammers, circuit boards, and connectors for coupling coils 13 and boards 15 to other devices. Numeral 17 are screws for fixing the yoke to carriage 10. These elements form what could be termed a head assembly.
Carriage 10 is machined and the assembly fixed onto its top including yoke 12 to which the permanent magnet 11, coils 13, circuit boards 15, and connectors 16 are attached. Head carriage 10 is held fast by screws 17. The typing hammers 14 include a comblike leaf spring 20 and a hammer pins 21 and are each actuated by and associated with a coil 13. Base 22 of leaf spring 20 is fixed to a mounting surface 23 at the front of carriage 10 by screws 24. Movements of yoke 12 in vertical and longitudinal directions are limited by surfaces 25 and 26, respectively. The surface 26 is defined by projections 27 extending in front of carriage 10 on the top thereof.
One disadvantage of this conventional arrangement is that machining head carriage 10 requires considerable time, making it expensive. Further, positioning yoke 12 when the printer is assembled is difficult, also requiring much time. In particular, the relative position between the typing hammers 14 and yoke 12 has a delicate effect on the punching or gapping force and the attractive force and the like and must be carefully adjusted to ensure accuracy of the printer. However, a tolerance is normally provided between the screw holes formed in yoke 12 of the head carriage 10 when yoke 12 is fixed to head carriage 10 by screws 17. This can result in misalignment in the relative position between typing hammers 14 and yoke 12, exerting a bad influence on accuracy of the printer. In order to counteract such effect, a thin metal foil which is capable of rectifying gap tolerance is normally interposed between yoke 12 and surface 26 for gap adjustment.
The present invention aims for its object at requiring no yoke positioning when the head carriage is machined and assembled and at making the head bank lightweight.
For achievement of such object, the head carriage 10 is molded of a resin and simultaneously, the head assembly including permanent magnet 11, yoke 12, coils 13, circuit boards 15, and connectors 16 integrally encapsulated therein. Thus, the necessity of screws 17 for securing and locating the yoke is avoided, and machining of the head carriage 10 is not required so that a highly dependable head bank may be made inexpensively.
Conventionally the circuit board 15 extends adjacent magnet 11 and weakens the magnetic force. According to a second embodiment cables are encapsulated in the carriage to directly connect the coils to an external control circuit, also simplifying assembly.